title: Constitutively active CaMKKα stimulates skeletal muscle glucose uptake in insulin-resistant mice in vivo.
abstract: In insulin-sensitive skeletal muscle, the expression of constitutively active Ca(2+)/calmodulin-dependent protein kinase kinase α (caCaMKKα) stimulates glucose uptake independent of insulin signaling (i.e., Akt and Akt-dependent TBC1D1/TBC1D4 phosphorylation). Our objectives were to determine whether caCaMKKα could stimulate glucose uptake additively with insulin in insulin-sensitive muscle, in the basal state in insulin-resistant muscle, and if so, to determine whether the effects were associated with altered TBC1D1/TBC1D4 phosphorylation. Mice were fed a control or high-fat diet (60% kcal) for 12 weeks to induce insulin resistance. Muscles were transfected with empty vector or caCaMKKα plasmids using in vivo electroporation. After 2 weeks, caCaMKKα protein was robustly expressed. In insulin-sensitive muscle, caCaMKKα increased basal in vivo [(3)H]-2-deoxyglucose uptake approximately twofold, insulin increased glucose uptake approximately twofold, and caCaMKKα plus insulin increased glucose uptake approximately fourfold. caCaMKKα did not increase basal TBC1D1 (Ser(237), Thr(590), Ser(660), pan-Thr/Ser) or TBC1D4 (Ser(588), Thr(642), pan-Thr/Ser) phosphorylation. In insulin-resistant muscle, caCaMKKα increased basal glucose uptake approximately twofold, and attenuated high-fat diet-induced basal TBC1D1 (Thr(590), pan-Thr/Ser) and TBC1D4 (Ser(588), Thr(642), pan-Thr/Ser) phosphorylation. In cell-free assays, CaMKKα increased TBC1D1 (Thr(590), pan-Thr/Ser) and TBC1D4 (Ser(588), pan-Thr/Ser) phosphorylation. Collectively, these results demonstrate that caCaMKKα stimulates glucose uptake additively with insulin, and in insulin-resistant muscle, and alters the phosphorylation of TBC1D1/TBC1D4.
authors.affiliation: Department of Kinesiology, East Carolina University, Greenville, NC.
authors.forename: J Matthew
authors.initials: JM
authors.lastname: Hinkley
authors.forename: Jeremie L
authors.initials: JL
authors.lastname: Ferey
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Brault
authors.forename: Cheryl A S
authors.initials: CA
authors.lastname: Smith
authors.forename: Laura A A
authors.initials: LA
authors.lastname: Gilliam
authors.forename: Carol A
authors.initials: CA
authors.lastname: Witczak
mesh_terms: D000818:Animals; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D051379:Mice; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D020690:GTPase-Activating Proteins; D007328:Insulin; D009687:Nuclear Proteins; C095906:Tbc1d1 protein, mouse; C505647:Tbc1d4 protein, mouse; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D005947:Glucose